Is 3D printing really food safe?
To cut a long story short: it depends.
The materials used in 3D printing are food safe. But it also depends on the details. We are talking about the FDM process, in which a thermoplastic (a material that becomes deformable under heat) is heated and rearranged. Another type of 3D printing is, for example, (M)SLA. Here, a resin is cured via UV irradiation. The FDM process is used for all current products.
The most common materials used in FDM 3D printing are, for example, PLA and PETG. PET(G) can be found in our daily lives: water and soda bottles are made out of PET [1]. PLA is also used for packaging food [2]. PLA is a compostable thermoplastic and well researched. As early as 1995, a study confirmed PLA's status as 'Generally Recognized As Safe' for food contact and storage [3].
From now on, however, the details come into play. PLA also has to be processed first. This is done in 3D printing via a thermoplastic process. Here, the material that comes into contact with food can get contaminated. Due to the high and permanent heat, particles consisting of non-food-safe materials can detach from other areas of the processing [4]. For this reason, only nozzles made of hardened steel are used in the manufacture of all products offered and not brass, as is usually the case.
Visible Layer lines at high layer thickness
The American FDA (Food And Drug Administration) and the European EFSA (European Food Safety Authority) have both included different materials and additives in their repertoire and approved them for the general public [5][6]. Generally speaking, it is recommended to coat the surfaces of 3D printed products with food safe sealants. These sealants are tested and approved. For 3D printed products that come in direct contact with moist food or directly in contact with the mouth, this is also strictly recommended.
Sources:
[1]: https://just3dp.com/blog/was-ist-der-unterschied-zwischen-pet-und-petg
[2]: https://www.sciencedirect.com/science/article/abs/pii/S0141813023006086
[3]: https://www.sciencedirect.com/science/article/abs/pii/027869159400145E,
[4]: https://www.wevolver.com/article/food-grade-3d-printing-is-pla-food-safe
[5]: https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=177
[6]: https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX%3A32011R0010
Other sources:
https://all3dp.com/2/food-safe-3d-printer-filament-best-brands/